The medical device industry produces a wide variety of electronic devices for treating patient medical conditions using electrical stimulation. Depending upon the medical condition, medical devices can be surgically implanted or connected externally to the patient receiving treatment. Clinicians use medical devices alone or in combination with drug therapies and surgery to treat patient medical conditions. For some medical conditions, medical devices provide the best, and sometimes the only therapy to restore an individual to a more healthful condition and a fuller life. Examples of implantable medical devices designed to deliver therapeutic electrical stimulation include neurological stimulators and spinal stimulators, as well as pacemakers and defibrillators.
Because implantable medical devices provide important, oftentimes life-sustaining medical care to patients from the power supplied by a single component power source, usually a battery, the ability to know the status of that power source is critical. When a power source's charge has nearly run down, the power source must either be replaced or recharged. The failure to do so could result in the untimely failure of the implantable medical device's ability to deliver therapy to the patient, with potential consequences up to and including patient death.
A common solution to avoid having to conduct surgery to replace a depleted power source is to make the power source of the implantable medical device rechargeable via transcutaneous transmission of energy. An external power supply is operatively coupled with the rechargeable power source of the implantable medical device, often through an inductive link, and charging current is delivered to the rechargeable power source until the rechargeable power source is replenished with charge. The implantable medical device may then continue to deliver therapy to the patient until the rechargeable power source has run down again and the process of recharging may then be repeated.